Simple to do, first make your .hgignore file:
gedit .hgignore
Add to this some basic syntax
syntax: glob
*.sql
*.gz
.DS_Store
public/cache/*
(basically here you're telling mercurial what file extensions and directories to ignore in your app's root directory)
Save & close the file (nano: CTRL+Y, VI:esc then ':wq' + enter), now when you do hg add . and hg commit it'll skip these files & directories and keep your repository clean storing only the things you need to worry about; the code.
